Process for producing alkylthioalkyl phosphonodithioic esters



United States Patent 3,463,840 PROCESS FOR PRODUCING ALKYLTHIOALKYLPHOSPHONODITHIOIC ESTERS Marion F. Botts, Independence, Mo., and Erik K.Regel, Mission, Kans., assignors to Chemagro Corporation, New York,N.Y., a corporation of New York No Drawing. Original application June24, 1966, Ser. No. 560,097. Divided and this application Jan. 3, 1968,Ser. No. 708,745

Int. Cl. C07f 9/40; A01n 9/36 US. Cl. 260--972 8 Claims ABSTRACT OF THEDISCLOSURE Compounds are prepared having the formula This application isa division of our copending application, Ser. No. 560,097, filed June24, 1966.

The present invention relates to the preparation ofalkylthioalkylphosphonodithioates and the use of such compounds asnematocides.

The reaction of aldehydes whith phosphorus trichloride has beeninvestigated by several authors, e.g., Fossek, Monatshefte vol. 5, page121 (1884), Kabashnik et al., Chem. Abst. vol. 44, page 7257 (1950), andConant et al., Jour. Amer. Chem. Soc., vol. 42, page 2337, vol. 43,pages 1928 and 10191, vol. 44, page 2530 and vol. 46, page 192.

Phosphorus trichloride adds on to aldehydes in an exothermic reaction attemperatures below 0 C., e.g., -50 C. to --70 C. The products obtainedare thermally unstable and are in equilibrium with phosphorustrichloride and aldehydes. The products have the formula:

where R is the residue of the aldehyde beyond the first carbonation.

This addition product, however, easily reacts with mercaptans. There arevarious possible competing reactions, including the following:

(a) mercaptal formation; (b) trithiophosphite formation; (c) reaction ofthe mercaptan with the addition product.

It has now been found that at temperatures well below 0 C., e.g., -70 to50 0., reaction (c) is the predominant reaction.

When mercaptans are reacted with a compound of Formula I in a 1:1 moleratio, the expected a-chloroalkylchloridophosphonothioates could not beisolated.

In similar fashion, when two moles of mercaptan were reacted with acompound of Formula I, the expectedaalkylthioalkylchloridophosphonothioates could not be isolated.

Instead, whether one mole or two moles of mercaptan were used, there wasisolated only alkylthioalkyldithiophosphonates in small yields. When atleast three moles of mercaptan are employed, thealkylthioalkyldithiophosphonates are obtained in good yields.

Alkylthioalkyldithiophosphonates are known compounds and are useful asdefoliants, Regal patent 3,193,- 372. The procedure for preparing suchcompounds in the Regal patent, namely reacting P01 with a hydrocarbonand a disulfide in the presence of a Friedel-Crafts catalyst, however,is relatively expensive considering the overall yields and reactionconditions employed.

Accordingly, it is an object of the present invention to develop a novelmethod for making alkylthioalkyldithiophosphonates.

Another object is to develop a novel method for making analogues ofalkylthioalkyldithiophosphonates wherein the alkyl thio group isreplaced by haloalkylthio.

A further object is to develop a method of preparing dithiophosphonateswhich cannot be synthesized by other routes.

An additional object is to develop a novel method for killing nematodes.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

It has now been found that these objects can be attained by preparingcompounds having the following formula:

where R R and R are alkyl (including cycloalkyl) and haloalkyl and R ishydrogen, alkyl, monohaloalkyl, aryl, haloaryl, and alkylthioalkyl.Preferably R R and R do not have over six carbon atoms.

Examples of compounds suitable as nematocides Within the invention areS,S-diethyl ethylthiomethane dithiophosphonate,

S,S-dimethyl l-rnethylthio ethane dithiophosphonate,

S,S-diethyl l-ethylthioethane dithiophosphonate,

S,S-dipropyl l-propylthioethane dithiophosphonate,

S,S-dibutyl l-butylthioethane dithiophosphonate,

S,S-dicyclohexyl l-cyclohexylthioethane dithiophosphonate,

S,S-dimethyl l-methylthiopropane dithiophosphonate,

S,S-diethyl l-ethylthiopropane dithiophosphonate,

S,S-dipropyl l-propylthio propane dithiophosphonate,

S,S-dimethyl l-rnethylthiobutane dithiophosphonate,

S,S-diethyl l-ethylthiobutane dithiophosphonate,

S,S-dihexyl l-hexylthiobutane dithiophosphonate,

S,S-dirnethyl l-methylthio 2-ethylhexane dithiophosphonate,

S,S-diethyl l-ethylthio 3-chlorobutane dithiophosphonate,

S,S-diethyl l-ethylthio 2-ethylthio butane dithiophosphonate,

S,S-dimethyl l-methylthio phenylmethane dithiophosphonate,

S,S-diethy1 l-ethylthio phenylmethane dithiophosphonate,

S,S-dibutyl l-butylthio phenylmethane dithiophosphonate,

S,S-diethyl l-ethylthio p-chlorophenylrnethane dithiophosphonate,

S,S-diethyl propylthio methane dithiophosphonate,

S,S-diethyl butylthiomethane dithiophosphonate,

S,S-dibutyl ethylthiomethane dithiophosphonate,

S,S-dibutyl butylthiomethane dithiophosphonate,

S,S-di (3-chloropropyl) 1-(3' chloropropylthio)ethane dithiophosphonate,

S,S-diethy1 l-ethylthio 3-chloropropane dithiophosphonate,

S,S-dimethyl 3-ethylthio propane dithiophosphonate,

S,S-dirnethyl-1-1nethylthio-rn-bromophenylmethane dithiophosphonate,

S,S-diamyl l-amylthio o-chlorophenylmethane dithiophosphonate,

S,S-diisopropyl l-isopropylthio p-tolylrnethane dithiophosphonate,

S,S-diethyl l-ethylthio Z-methylpropane dithiophosphonate,

S,S-dimethyl l-methylthio 2',6'-dichlorophenylmethane dithiophosphonate,

S,S-dimethyl-1,3- di(ethylthio) propane dithiophosphonate. As aldehydesfor the reaction, there can be used formaldehyde (including trioxane andparaformaldeacetaldehyde,

propioualdehyde,

butyraldehyde,

isobutyraldehyde,

valeraldehyde,

hexaldehyde,

3-methylthio propionaldehyde,

2-ethylhexanal,

Z-chlorobutyraldehyde,

3-chlorobutyraldehyde,

2-ethylthiobutyraldehyde,

benzaldehyde,

Z-butylthioacetaldehyde,

p-chlorobenzaldehyde,

o-chlorobenzaldehyde,

m-bromobenzaldehyde,

2,6-dichlorobenzaldehyde,

3-ethylthiopropionaldehyde,

3-chloropropionaldehyde,

p-tolualdehyde,

o-tolualdehyde,

2,4,6-trichlorobenzaldehyde,

3-ethylthiopropionaldehyde.

As mercaptans there can be used methyl mercaptan, ethyl mercaptan,propyl mercaptan, butyl mercaptan, amyl mercaptan, cyclohexyl mercaptan,3-chloropropyl mercaptan, isobutyl mercaptan, secondary butyl mercaptan,octyl mercaptan, 2-chlorobutyl mercaptan, 3-bromobutyl mercaptan.

If a mixture of mercaptans are employed for reaction with the aldehydethe product obtained in Formula II will be a mixture in which R R and Rneed not be alike. However, if a single mercaptan is used, then R R andR, will be identical. R in the formula is dependent upon the aldehydeemployed.

The preparation of alkylthioalkyl dithiophosphonates by the reaction ofat least three moles of mercaptan with 1 mole of aldehyde givespatricularly good yields with lower aliphatic aldehydes having at leasttwo carbon atoms, the yields in some cases exceeding 80%. Aromaticaldehydes also have been found to give good yields of the desiredproduct and rnonohalo aliphatic aldehydes have been found to give yieldsup to 60%.

While more than 3 moles of mercaptan, e.g. 4, 5 or 6 moles, can be usedper mole of aldehyde there generally is no advantage in doing so and theexcess mercaptan must be recovered.

The yields of the alkylthioalkyl dithiophosphonates using formaldehydeas the aldehyde generally are low. This is also the case when employingalkylthio aliphatic aldehydes, e.g. 3-ethylthiobutanal.

The reaction does not work with aldehydes having a,B-aliphaticunsaturation. Chloral was inoperative and 4 formed the mercaptal insteadunder the described reaction conditions.

The present invention is suitable for preparing dithiophosphonates whichcannot be synthesized by other routes or which can be synthesized onlywith difficulty by other methods.

The reaction of the aldehyde with mercaptan can be carried out in thepresence of a solvent, e.g. benzene, toluene, carbon tetrachloride,chloroform or the like although this is not essential.

The general procedure employed to prepare the alkylthioalkyldithiophosphonates was as follows:

GENERAL PROCEDURE Phosphorus trichloride was placed in a three neckedflask equipped with a thermometer, stirrer, condenser and droppingfunnel. External cooling Was provided by an acetone-Dry Ice bath. At 70C. the aldehyde was added slowly while agitating the phosphorustrichloride. The temperature was kept at -70 C. by adjusting theaddition rate of the aldehyde. After addition of the aldehyde wascompleted the reaction mixture was agitated for 1 hour at -70 C.

Then the mercaptan was added dropwise at 70 C. to 60 C. The reactionmixture was then allowed to Warm up to 40 C. where hydrogen chloridebegan to evolve, and the reaction mixture was agitated for 1 hour afterthe addition was completed.

Finally the reaction mixture was slowly brought up to room temperatureand without agitation allowed to stand for several hours. The crudeproduct was then Washed with water until neutral, dried and distilled ina high vacuum.

In order to separate small amounts of mercaptals from the desireddithiophosphonate, the crude product is preferably redistilled orfractionated over a small Vigreaux column.

Example 1 Using the General Procedure 1 mole (137.39 grams) ofphosphorus trichloride was reacted with 30 grams of paraformaldehyde(equivalent to 1 mole of formaldehyde). There was then added dropwise 3moles (186 grams) of ethyl mercaptan. The product was S,S-diethylethylthiomethane dithiophosphonate B.P. 120 C., n 1.5652, Code No. 6480,yield 19%.

Example 2 The same product as that of Example 1 was prepared by analternate procedure, namely, reacting 1 mole of sodium ethyl mercaptidewith 1 mole of S,S-diethyl chloromethane diethiophosphonate, filtered toremove sodium chloride and washed with water to produce S,S-diethylethylthiomethane dithiophosphonate, B.P. 123 C., n 1.5646. This productwas given the Code No. 6435 and was obtained in a yield of 29%.

Example 3 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of acetaldehyde. There was then added 3 moles ofmethyl rnercaptan. The prod uct was S,S-dimethyl methylthioethanedithiophosphonate B.P. C., 11 1.5996, Code No. 6483, yield in excess of70%.

Example 4 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of acetaldehyde. There was then added dropwise 3moles of ethyl mercaptan. The product was S,S-diethyl ethylthioethanedithiophosphonate, BR 119 C., 11 1.5568, Code No. 6482, yield 70%.

Example 5 Using the General Procedure 1 mole of phosphorus trichloridewas reacted With 1 mole of acetaldehyde. There was then added dropwise 3moles of propyl mercaptan.

The product was S,S-dipropyl propylthioethane dithiophosphonate, B.P.132 C., n 1.5385, Code No. 6443, yield 65%.

Example 6 Using the general Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of acetaldehyde. There was then added dropwise 3moles of butyl mercaptan. The product was S,S-dibutyl butylthioethanedithiophosphonate, B.P. 155 C., 11 1.5283, Code No. 6438, yield 68%.

Example 7 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of acetaldehyde. There was then added dropwise 3moles of cyclohexyl mercaptan. The product was S,S-dicyclohexylcyclohexylthioethane dithiophosphonate, a high boiling oil, 11 1.5692,Code No. 6513, yield 82%.

Example 8 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of propionaldehyde. There was then added 3 molesof methyl mercaptan. The product was S,S-dimethyl l-methylthiopropanedithiophosphonate, B.P. 120 C., 11 1.5850, Code No. 6514, yield 33%.

Example 9 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of propionaldehyde. There was then addeddropwise 3 moles of ethyl mercaptan. The product was S,S-diethyll-ethylthiopropane dithiophosphonate, B.P. 120 C., n 1.5536, Code No.6518, yield 30%.

Example 10 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of propionaldehyde. There was then addeddropwise 3 moles of propyl mercaptan. The product was S,S-dipropyll-propylthiopropane dithiophosphonate, B.P. 140 C., 11 1.5363, Code No.6519.

Example 11 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of butyraldehyde. There was then added dropwise3 moles of methyl mercaptan. The product was S,S-dimethyll-rnethylthiobutane dithiophosphonate, B.P. 120 C., n 1.5700, Code No.6515, Yield 20%.

Example 12 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of butyraldehyde. There was then added dropwise3 moles of ethyl mercaptan. The product was S,S-diethy1l-ethylthiobutane dithiophosphonate, B.P. 130 C., 21 1.5475, Code No.6440, yield 50%.

Example 13 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of 2-ethylhexanal. There was then added 3 molesof methyl mercaptan. The product was S,S-dimethyl1-methylthio-2-ethyl-hexane dithiophosphonate, B.P. 128 C., n 1.5478,Code No. 6441, yield 13%.

Example 14 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of 3-chlorobutyraldehyde. There was then addeddropwise 3 moles of ethyl mercaptan. The product was S,S-diethyl1-ethylthi0-3- chlorobutane dithiophosphonate, B.P. 145 C., 11 1.5550,Code No. 6476, yield 22%.

Example 15 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of 3-ethylthiobutyraldehyde. There was thenadded dropwise 3 moles of ethyl mercaptan. The product Was S,S-diethyll-ethylthio 3- ethylthiobutane dithiophosphonate (also calledS,S-diethyl 1,3 di(ethylthio) butane dithiophosphonate), B11 169 C., n1.5580. Code No. 6477, yield 22%.

Example 16 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of benzaldehyde. There was then added dropwise 3moles of methyl mercaptan. The product was S,S-dimethyl l-methylthiophenyl-methane dithiophosphonate, M.P. C., Code No. 6516.

Example 17 Using the general Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of benzaldehyde. There was then added dropwise 3moles of ethyl mercaptan. The product was S,S-diethyl l-ethylthiophenylmethane dithiophosphonate, B.P. C., n 1.6015, Code No. 6450, yield30%.

Example 18 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of benzaldehyde. There was then added dropwise 3moles of butyl mercaptan. The product was S,S-dibutyl l-butylthiophenylmethane dithiophosphonate, a heavy oil 11 1.5563, Code No. 6517,yield 94%.

Example 19 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of p-chlorobenzaldehyde. There was then addeddropwise 3 moles of ethyl mercaptan. The product was S,S-diethyll-ethylthio p-chlorophenylmethane dithiophosphonate, B.P. 170 C., 111.6048, Code No. 6921.

Example 20 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of acetaldehyde. There was then added dropwise 3moles of 3-chloropropyl mercaptan. The product was S,S-di(3'-ch1oropropyl) 1,3- chloropropylthioethane dithiophosphonate, a heavyoil, Code No. 6444.

Example 21 Using the General Procedure 1 mole of phosphorus trichloridewas reacted with 1 mole of 3-ethylthio propionaldehyde. There was thenadded 3 moles of methyl mercaptan. The product was S,S-dimethyll-methylthio 3-ethylthiopropane dithiophosphonate, a heavy oil, Code No.6445.

Example 22 The procedure of Example 3 was repeated. The product wasgiven the Code No. 6436.

Example 23 The procedure of Example 4 was repeated. The product wasgiven the Code No. 6437.

Example 24 The procedure of Example 9 was repeated. The product wasgiven the Code No. 6439.

Example 25 1 mole of sodium propyl mercaptide was reacted with 1 mole ofS,S-diethyl chloromethane dithiophosphonate using the procedure ofExample 2 to produce S,S-diethyl propylthiomethane dithiophosphonate asan oil, Code No. 6470.

Alternatively, Code No. 6470 can be prepared in low yields by theGeneral Procedure reacting 1 mole of phosphorus trichloride with 30grams of paraforrnaldehyde (1 mole of formaldehyde) followed by thedropwise addition of a mixture of 2 moles of ethyl mercaptan and 1 moleof propyl mercaptan.

Example 27 1 mole of sodium butyl mercaptide was reacted with 1 mole ofS,S-diethy1 chloromethane dithiophosphonate using the procedure ofExample 2 to produce S,S-diethyl butylthiomethane dithiophosphonate asan oil, Code No. 6471.

Alternatively, Code No. 6471 can be prepared in low yields by theGeneral Procedure reacting 1 mole of phosphorus trichloride with 30grams of paraformaldehyde followed by the dropwise addition of a mixtureof 2 moles of ethyl mercaptan and 1 mole of butyl mercaptan.

Example 28 1 mole of sodium ethyl mercaptide was reacted with 1 mole ofS,S-dibutyl chloromethane dithiophosphonate using the procedure ofExample 2 to produce S,S-dibutyl ethylthiomethane as an oil, Code No.6472.

Alternatively, Code No. 6472 can be prepared in low yields by theGeneral Procedure reacting 1 mole of phosphorus trichloride with 30grams of paraformaldehyde followed by the dropwise addition of a mixtureof 2 moles butyl mercaptan and 1 mole of ethyl mercaptan.

Example 29 1 mole of sodium butyl mercaptide was reacted with 1 mole ofS,S-dibutyl chloromethane dithiophosphonate using the procedure ofExample 2 to produce S,Sdibutyl butylthiomethane dithiophosphonate as anoil, Code No. 6473.

Alternatively, Code No. 6473 can be prepared in low yields by theGeneral Procedure reacting 1 mole of phosphorus trichloride with 30grams of paraformaldehyde followed by the dropwise addition of 3 molesof the butyl mercaptan.

The compounds of the present invention can be used alone as nematocidesbut it has been found desirable to apply them to the pest, e.g. to thesoil habitat of nematodes, together with inert solids to form dusts, or,preferably water. There can also be added surface active agents andinert solids in such liquid formulations. Desirably, 0.05 to 1% byweight of surface active agent is employed. The active ingredient can befrom 0.01 to 95% by weight of the entire composition in such cases.

In place of water there can be employed organic solvents as carriers,e.g., hydrocarbons such as benzene, toluene, xylene, kerosene, dieseloil, fuel oil, and petroleum naphtha, ketones such as acetone, methylethyl ketone and cyclohexanone, alcohols, e.g., ethanol, isopropanol andamyl alcohol, etc.

The nematocides of the present invention can also be applied with inertnematocidal adjuvants or carriers such as talc, pyrophyllite, syntheticfine silica, Attaclay, kieselguhr, chalk, diatomaceous earth, lime,calcium carbonate, bentonite, fullers earth, cottonseed hulls, wheatflour,

soybean flour, pumice, tripoli, wood flour, walnut shell flour, redwoodflour and lignin.

It is frequently desirable to incorporate a surface active agent in thepesticidal compositions of thi invention. Such surface active agents,i.e., wetting agent, are advantageously employed in both the solid andliquid compositions. The surface active agent can be anionic, cationicor nonionic in character.

Typical classes of surface active agents include alkyl sulfonate salts,alkylaryl sulfonate salts, alkyl sulfate salts, alkylamide sulfonatesalts, alkylaryl polyether alcohols, fatty acid esters of polyhydricalcohols and the alkylene oxide addition products of such esters, andaddition products of long chain mercaptans and alkylene oxides. Typicalexamples of such surface active agents include the sodium alkyl benzenesulfonates having 14 to 18 carbon atoms in the alkyl group,alkyl-phenol-ethylene oxide condensation products, e.g.,p-isooctylphenol condensed with 10 ethylene oxide units, soaps, e.g.,sodium stearate and potassium oleate, sodium salt of propyluaphthalenesulfonic acid, (di-Z-ethyl hexyl) ester of sodium sulfosuccinic acid,sodium lauryl sulfate, sodium salt of the sulfonated monoglyceride ofcocoanut fatty acids, sorbitan sesquioleate, lauryl trimethyl ammoniumchloride, octadecyl trimethyl ammonium chloride, polyethylene glycollauryl ether, polyethylene esters of fatty acids and rosin acids, e.g.,Ethofat 7 and 13, sodium N-methyl- N-oleyl-taurate, Turkey red oil,sodium dibutylnaphthalene sulfonate, sodium lignin sulfonate (MarasperseN), polyethylene glycol stearate, sodium dodecylbenzene sulfonate,tertiary dodecyl polyethylene glycol thioether (Nonionic 218), longchain ethylene oxide propylene oxide condensation products, e.g.,Pluronic 61, sorbitan monolaurate, polyethylene glycol ester of tall oilacids, sodium octylphenoxyethoxyethyl sulfate, tris (polyoxyethylene)sorbitan monostearate (Tween 60), sodium dihexyl sulfosuccinate.

The solid and liquid formulations can be prepared by any of theconventional methods. Thus, the active ingredient can be mixed with thesolid carrier in finely divided form in amounts small enough to preservethe free-flowing property of the final dust composition.

In commercial practice the compositions containing the nematocides ofthe present invention are applied to the soil infested with nematodes.

In the following examples or tables illustrating nematocidal activitythe compounds of the invention were formulated as wettable powdersconsisting of 50% of the compound being tested, 46% Hi-Sil 233(ultrafine silica), 2% Marasperse N (sodium lignin sulfonate) and 2%Pluronic L61 (polyethylene oxide-propylene oxide adduct molecular weightabout 1000). This Wettable powder is hereinafter designated asFormulation A.

Example 30 The saprophytic nematode tests were carried out in water asthe medium with Panagrellus and Rhabditis spp. at room temperatureutilizing Formulation A. The results are recorded as percent kill at theindicated dosages in parts per million after a 4 day incubation period.A 10% kill is merely the same amount of kill as occurs with a blanksample.

TABLE I NESA at p.p.m.

Example 100 50 10 Example 31 Some of the compounds were also testedagainst parasitic nematodes employing Formulation A. The nematodeemployed was Meloidogyne spp. and the procedure was a 10 day contacttest carried out in a Water-agar medium in the presence of tomato rootsat room temperature.

The results are given on a -10 scale where 0 indicates the presence ofsevere knotting, i.e. no effectiveness and 10 indicates no knots, i.e.100% etfectiveness. The dosages are at the indicated concentrations oftest compound in parts per million.

TABLE II NEMA at p.p.m.

Compound Example 50 25 12 6 2 10 10 7.6 5 26 1o 0 0 27 10 1o 0 0 2s 8 00 0 29 5 0 o 0 22 8.8 0 0 0 2a 8.8 0 0 0 5 10 10 10 8.8 24 8.8 0 o 0 910 0 0 0 We claim: 1. A process of preparing a compound having theformula (|)/SR: RiSfilHl Ra SR4 where R R and R are lower alkyl,monochloro lower alkyl or mono bromo lower alkyl and R is hydrogen,lower alkyl, mono chloro lower alkyl, phenyl, chlorophenyl, bromophenyl,methyl phenyl or lower alky1thio alkyl comprising (1) reacting 1 mole ofphosphorus trichloride with one mole of an aldehyde having the formula RCHO at a temperature not over -40 C., and (2) reacting this product with3 moles of a mercaptan or mixture of mercaptans having the formula R SH,R SH and R SH at a temperature not over C.

2. A process according to claim 1 wherein reactions (1) and (2) arecarried out at a temperature between -70 C. and -40 C.

3. A process according to claim 2 wherein reactions (1) and (2) arecarried out at a temperature between 70 C. and C., R R and R are loweralkyl and R is alkyl of 1 to 3 carbon atoms.

4. A process according to claim 1 wherein R R and R are the same.

5. A process according to claim 4 wherein reactions 1) and (2) arecarried out at a temperature between C. and -40 C.

6. A process according to claim 4 wherein R R and R are lower alkyl.

7. A process according to claim 6 wherein R is alkyl of 1 to 3 carbonatoms.

8. A process according to claim 6 wherein R is phenyl.

References Cited UNITED STATES PATENTS 8/1941 Stevens et al. 260972 XR10/1967 Regel 260-972 XR US. Cl. X.R.

